Electromagnetic hammer



y 6, 1941- c. H. HULBERT 2,241,364

ELECTROMAGNETIC HAMMER Filed Jan. 22, 1938 Patented May 6, 1941 UNITED STATES PATENT OFFICE ELECTROMAGNETIC HAMMER Clinton Horace Hulbert, Venice, Calif.

Application January 22, 1938, Serial No. 186,406

4 Claims.

My invention relates to improvements, pertaining to electro-magnetic hammers adapted for various purposes, such as demanded in mining hammers, pavement breakers, tamping and other useful purposes to that effect.

An object of my invention is to provide improvements, so as to increase the effectiveness and operating etficiency of the hammer, by concentrating the greater part of the operative energy to the hammer tool.

One of the objects, to increase the efiiciency is to have a cored buffer armature in a two field electro-magnetic hammer, in which part of the core section is a bearing for the hammer shaft and the other part of the core acts as a tool socket bearing; the buffer armature has dimensions, so as to induce a relatively large magnetic contact surface area with a magnetic hammer armature; the outer end of the hammer armature telescopes freely, inside the pole face of the field, which means allows more energy to be applied to the hammer tool and also allows the hammer armature to self adjust itself in various stroke lengths.

Another object to increase the efficiency, is to keep the weight of the buffer armature substantially reduced, yet at the same time, to retain sufficient field surface area for the magnetic lines of force necessary for the proper working operation of a relative heavier hammer armature, I

which means allows for a greater flexibility in the giving-in, when the hammer armature is at a striking face contact with the buffer armature and also allows a more eflicient rebounding response of the hammer armature, when released, and overcomes excess dead-pounding loss upon the magnetic armature faces.

Another object, to increase the efficiency, is confining the hammer and buffer armatures within and about the field pole faces, which are projected inward in such a manner, so as to allow the magnet windings to be set back, and overlap the projected pole faces and to have the varying armature gaps directly under the said windings.

Another object, to improve the efficiency, is to have more laminated iron area in the section of the hammer armature that contacts the buffer armature field side, so as to derive a greater electrical input load for the hammer stroke.

A further object, is to conceal the counterbalancing springs and the bearing within the frame ends and hollowed section of the hammer annature, and to cap over the outer end of the hammer shaft to prevent dirt from entering the bearings and to retain the lubricant.

Another object, is to provide for improved construction of my hammer handles which consists of two stiff springs, welded upon the frame end, and extending outward, as handles; these springs are of sufilcient tension, so as to support the weight of the hammer, without undue bending, yet allow spring buoyancy at the hammer ends; the spring handle ends are preferably covered with a piece of rubber hose, said improved construction aids to absorb the stroke vibration to the operator's hands.

My invention has other objects, pertaining to improvements in my electro-magnetic hammer, which appear hereinafter in detailed description and in connection with accompanying drawing.

Figure 1 is a vertical cross section of one embodiment of this invention; namely, my double field electro-magnetic hammer.

Figure 2 is a schematic outline pertaining to Figure 1, to demonstrate the relative position of the magnet wire windings.

Figure 1 is a vertical section view of one em bodiment of my invention, having two separate magnetic field circuits, in which numeral l is a non-magnetic hammer shaft, preferably an alloy of nickel, chromium and iron. The hammer shaft has welded thereto at its end a hardened steel tip 2, and intermediate its ends a collar 3, preferably of non-magnetic stainless steel. The shaft is further provided with a threaded section 4 to which the hammer armature 5 is secured. The hammer armature 5 is built up of various width strips of iron punchings, forming individual pie-like divisions and arranged to pro vide lengthwise air ducts throughout the structure. Each individual iron punching is welded to a hollow core 6 to form a lengthwise laminated armature assembly. The weldings are at positions, which do not interfere with the active magnetic operative lines of force. A nut I and a heavy lock washer 8 substantially supports the threaded hammer armature 5 upon the hammer shaft I. The shaft I is reduced in size at l0 and threaded at H and the nut I2 is held from tuming, by pin l3. A bearing I4 is supported by bracket 15, in such a manner, so as to allow space for the outward compression spring l6 and the inward compression spring H, to be concealed within the frame I8, which allows the shaft end and nut l2 to be capped over with cap IS. A lubricant, preferably grease, is applied inside at the shaft end, and about nut i2; the frame end has various air vents 20 for air circulation.

Handles 2! are an improved feature, by being constructed of two stiff springs, welded upon the frame end [8, and extending outwardly, the springs are of sufiicient strength to support the weight of the hammer, without undue bending, yet allow spring buoyancy at the handle ends, which are covered with a rubber tube or hose 22, which slips over the spring ends, by which to absorb the stroke vibrations from the hands of the operator. The hammer armature 5 is self adjusting in its stroke length which operates up to two and one half inches for a four inch armature. At each field end of the hammer structure are two lengthwise laminated steel collars, 23 and 23 composed of lengthwise punched strips, which are bound together by two independent welds Z='l and 25, all the way around; the two collars 23 and 23' have inwardly projecting flanges 25 and 21, which also aid to compactly hold the magnetic windings in place, and allows the magnetic windings to be directly over the gap ends of the hammer armature. The buffer armature 28 is built up similarly to the hammer armature 5, with air vents throughout the lengthwise laminated iron structure, forming a core of mild steel 29, which is threaded at 30, and assembled upon the mild steel tube 3!; the hollow core 29 is threaded and welded to tube 3! to increase its strength. A weld is made on the outside of the buffer armature inside of the groove 32, all the way around, which also increases the strength of the baffle armature 28. The tube 3| also acts as a tool socket for tool 33; the tube socket 3! is assembled inside a bearing 34, attached upon the frame end 35, having various air vents 36; the tube socket end is threaded at 31 for assembly of nut Inside and against the frame end 35 and the buffer armature is a compression spring 39. Mounted about the frame end 35 and over the buffer bearing 34, is an extended bearingsupport 40, for holding a hexagon bearing 41, for loosely inserting a hexagon tool 33; a flange 42 prevents the tool from further entry and a guide 43 prevents the tool 33 from dropping out of the hammer socket. The dividing center field pole 45, between the two fields A and B, has extended flanges 45 and 55', to increase the field surface area and to hold the magnet wire windings firmly in place; center pole 44 is built up alternately of lengthwise laminated iron strips of two sizes and interwoven between the narrow and longer strips of the outer field 46, and welded at several places 4'! and 48; several soft iron rods, preferably of a pure grade of iron such as Armco brand, either round or square, are assembled between the lengthwise outer field laminations, before Welding same together; these rods are threaded at both ends 59 and case hardened, (eight rods do very well for a four inch hammer). The two frame ends l8 and 35 are held together substantially by various bolts 5!] upon rod ends 49.

In field A of the hammer side, are two magnet windings 5| and 52, and in the other field B are two other magnet windings 5-3 and 54. The outlet cables pass through an open part of the laminated section, which has been allowed for, in the field structure 45.

Since field A, the hammer side, requires a greater load current, the magnet windings 5| and 52 may be larger than the windings 53 and 54 in field B.

Figure I represents my double field hammer for a four inch armature, some of the details pertaining to the construction of this hammer have been included in my prior application for Letters of Patent, Ser. Nos. 139,528, 139,529 Apr. 28, 1937, and 174,180 Nov. 12, 1937. One of the improved features of my hammer Fig. 1 is to construct the head part of the hammer armature 5, with a greater laminated iron area, so as to allow relatively heavy lines of magnetic force to pass to the hammer armature 5 from the relative large center pole field area 44 and 45 and through the large face area 56 of the buffer armature 28 and through a large pole face area 21, as the field A demands a greater amount of energy to cause a powerful hammer stroke, upon the drill steel 33, while the other field B, which opens the hammer armature 5 and requires less energy, telescopes in and out of the field pole face 25, mechanically unobstructed, to allow short or longer strokes, thus concentrating the hammer energy mainly in field A; which allows the hammer armature to self adjust its stroke length correspondingly to the input energy and frequency of the applied currents. Another improved feature is in my buffer armature 28 I originally had my buffer armature, as in my three prior applications for Letters Patent, hollowed out, at its outer section, for a spring assembly inside, and allow the buffer armature to project further inward, which is satisfactory for some types of my hammers, but I find that I can derive further increased efficiency, by eliminating the said hollow section, and. instead concentrate the dimensions of my buffer armature, as in numeral 28; through this improvement, I derive a greater amount of useful laminated iron, which causes a shorter path for the induced lines of magnetic force, to travel through the relative large field pole 2'1 and that of the large face area of the hammer armature 5; another improvement derived by concentrating the dimensions of my buffer armature is, that it reduces the weight of same, which allows a greater freedom in the rebounding action, and overcomes detrimental dead-weight loss pounding upon the baffle and hammer armature faces. I wish to enlarge upon the merits of these improved features in my hammer Fig. 1, which might appear unimportant and of minor detail; The air gaps and 59 between armature 5 and buffer armature 60 and pole flanges 26 are seen to be opposite the magnetic windings and re duce the impedance of the windings and permit maximum magnetizing current to flow therein. I strive to derive as large a magnetic face and inductive area as is practical, and to shorten the magnetic lines of induction about the armature faces, and I also slightly increase the faces by tapering the armatures at forty-five degree angle. An improved feature is also derived by having the inverted field fiange pole faces 2! completely overlapping the buffer armature at 60, which increases the efficiency at the stroke end.

What I claim is:

1. An electrically operated unit for imparting intermittent reciprocating movements, comprising an outer longitudinal frame member, solenoid and field members mounted within said frame, said solenoid bein mounted longitudinally of the frame intermediate the field members, a handle at the upper end, a shaft in the frame coaxial therewith, an armature mounted on said shaft so as to reciprocate therewith, bearing brackets having bearing surfaces therein secured to said frame at each end thereof, a tube slidably supported in the lower bearing bracket coaxial with the frame, a buffer armature secured to said tube adjacent the lower field member so as to form therewith a continuation of the magnetic circuit and having a recess therein for engagement with the armature, a spring means positioned between said buffer armature and lower bearing bracket urging said balfie armature upwardly towards the limit of its movement, whereby the buffer armature may regulate the length of the stroke of the reciprocating member, aid in absorbing the impact between armature members, and present a large surface area between the cooperating magnetic parts to provide an increased attractive force.

2. An electrically operated unit for imparting intermittent reciprocating movements, comprising an outer longitudinal frame member, solenoid and field members mounted within said frame, said solenoid being mounted longitudinally of the frame intermediate the field members, a handle at the upper end, a reciprocable shaft resiliently mounted in the frame coaxial therewith, an armature mounted on said shaft so as to reciprocate therewith and having a conical 10wer portion, bearing brackets having bearing surfaces therein secured to said frame at each end thereof, a tube slidably supported in the lower 7 bearing bracket coaxial with the frame, a buffer armature secured to said tube adjacent the lower field member so as to form therewith a continuation of the magnetic circuit and having a conical recess therein for engagement with the armature, a spring means positioned between said buffer armature and lower bearing bracket urging said buffer armature upwardly towards the limit of its movement, whereby the buffer armature may regulate the length of the stroke of the reciprocating member, aid in absorbing the impact between armature members, and present a large surface area between the cooperating magnetic parts to provide an increased attractive force.

3. An electrically operated unit for imparting intermittent reciprocating movements, comprising an outer longitudinal frame member, solenoid and field members mounted within said frame, said solenoid being mounted longitudinally of the frame intermediate the field members, a handle at the upper end, a shaft in the frame coaxial therewith, an armature mounted on said shaft so as to reciprocate therewith, bearing brackets having bearing surfaces therein secured to said frame at each end thereof, a tube slidably supported in the lower bearing bracket coaxial with the frame, means to adjust the normal position of said tube on said frame, a buffer armature secured to said tube adjacent the lower field member so as to form therewith a continuation of the magnetic circuit, said buffer armature being opposite an end of said hammer armature and having a recess for engagement with the hammer armature, a spring means positioned between said buffer armature and lower bearing bracket urging said buffer armature upwardly towards the limit of its movement, whereby the buffer armature may regulate the length of the stroke of the reciprocating member, aid in absorbing the impact between armature members, and present a large surface area between the cooperating magnetic parts to provide an increased attractive force.

4. An electrically operated unit for imparting intermittent reciprocating movements, comprising an outer longitudinal frame member, solenoid and field members mounted within said frame, said solenoid being mounted longitudinally of the frame intermediate the field members, a pair of coil spring handles at the upper end, a tool clutch at the lower end, a shaft in the frame coaxial therewith, an armature mounted on said shaft so as to reciprocate therewith, a recess in said armature, a spring in said recess engaging said frame adapted to bias said shaft downwardly, bearing brackets having bearing surfaces therein secured to said frame at each end thereof, the upper of said brackets having a recess for a lubricant, a spring in said last recess engagin said shaft adapted to bias said shaft upwardly, a cover on said bracket, a tube slidably supported in the lower bearing bracket coaxial with the frame, a buffer armature secured to said tube adjacent the lower field member so as to form therewith a continuation of the magnetic circuit and having a recess therein for engagement with the arma ture, a spring means positioned between said buffer armature and lower bearing bracket urging said buffer armature upwardly towards the limit of its movement, whereby the buffer armature may regulate the length of the stroke of the reciprocating member, aid in absorbing the impact between armature members, and present a large surface area between the cooperating magnetic parts to provide an increased attractive force.

CLINTON H. HULBERT. 

